The Unforgivable Sin
There is only one Unforgivable Sin: "when someone blasphemes against the Holy Spirit."
It is a sin that will never be forgiven by God, no matter what the person does after.
Many worry they've committed the "unforgivable sin". I hear people ask this question all the time. I even heard one woman ask this question at a Bible study: "Were Adam and Eve kicked out of the garden because they had sex, which was the unforgivable sin? Was the forbidden fruit, really 'having sex' symbolized by a tree-fruit?". Btw the woman was Catholic. While this is obviously an extreme case, there are many similar concerns out there for sins of the flesh.
To put your mind at ease, Jesus made it clear that the unforgivable sin is a spiritual one, that all sorts of sins of the flesh are forgivable.
Jesus said: 28 Truly I tell you, people can be forgiven all their sins and every slander they utter, 29 but whoever blasphemes against the Holy Spirit will never be forgiven; they are guilty of an eternal sin.”
30 He said this because they were saying, “He has an impure spirit.”
There you have it. Jesus stressed that the only sin that is unforgivable is a spiritual one - when someone blasphemes against the Holy Spirit.
How is the Unforgivable Sin Committed?
It is when a person is sure that another person is filled with the Holy Spirit, but calls them demon possessed. Specifically in these verses above, Jesus was referring to the Jewish "teachers of the law" that were there. He knew they recognized Him as the Messiah, but did not want to acknowledge Him. Instead they called Him demon-possessed. Which means they called the Holy-Spirit inside Jesus a "demon". Which is not a commonly committed sin today; usually people worry about sins of the flesh. So rest assured, it is unlikely that you did anything like this, and therefore your sins will be forgiven when you repent, turn to God and accept Jesus as the Christ and savior, learn His commands, and keep them. Then start growing spiritually on the right path.
The same message of the unforgivable sin also appeared in these two references:
Therefore, I tell you, people will be forgiven every sin and blasphemy, but the blasphemy against the Spirit will not be forgiven. Whoever speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age or in the one to come.
1 John 5:16-17
“If anyone sees a fellow believer committing a sin that doesn’t lead to death, he should ask, and God will give life to him — to those who commit sin that doesn’t lead to death. There is sin that leads to death. I am not saying he should pray about that. All unrighteousness is sin, and there is sin that doesn’t lead to death.”
And the same blaspheme message of unforgivable sin also appeared in the Old Testament:
1 Samuel 3:13-14
God said through the prophet Samuel: “For I told him that I would judge his family forever because of the sin he knew about; his sons blasphemed God, and he failed to restrain them. Therefore I swore to the house of Eli, ‘The guilt of Eli’s house will never be atoned for by sacrifice or offering.’ ””
So how does one commit the unforgivable sin? It is a deliberate act by a mature person who knows exactly what they're saying. It is not for example when an immature or young person says things in anger without knowing what they're really saying. Let's examine the above verses again. These were Jewish Pharisees who just witnessed Jesus perform a miracle of driving out a demon from a man. Then they called Jesus demon-possessed. In other words, they knew it was a Spirit from God inside Jesus but still called Him a demon.
To apply this to today, it would have to be something like, someone has performed a miracle in the name of Jesus. And you called him demon-possessed. Not that likely to happen given the current zero number of people performing miracles in the name of Jesus. Of course this will present a dilemma in the future for those who are alive when the anti-Christ shows up on the scene, and starts performing wonders in front of people. This is why we should all keep seeking God, so we recognize the false prophets and not fall in that trap.
I see many internet articles from fairly good Christian sources explaining the unforgivable sin as, "one who lashes out at the Holy Spirit within one's self". This is not good explanation. No person on earth has the Holy Spirit inside of them unless they specifically pray to God the Father and ask for Him. The Bible verses were clear about describing this sin as someone blaspheming against the Holy Spirit in others, not in their own self. Trying to connect those who become Atheists to the unforgivable sin is not the right explanation. It's two different things. The next section below addresses this.
Related Unforgiveness Clarifications
There is another way to become permanently unforgiven in today's world, and is happening often in young generations. If a person decides "there is no God" - he/she don't believe in God, and become an atheist for example. Then never turn back to God, and dies as an atheist? This person cannot be forgiven by God. This person basically cut the cord with God. God cannot force Himself on them. This person essentially sent himself/herself to hell. Remember, James 4:8 Come near to God and He will come near to you. And the opposite is true - move away from God and He will move away from you. And when God moves away from you, you have nothing left except utter darkness and torment; you'd be heading in that direction.
But if this atheist decided to turn back to God and become a true Christian, then God will accept them. Which is not the same for the one who committed the "unforgivable sin". A person who truly committed the unforgivable sin, does not even have the ability to turn back to God. If you were an atheist, and now find yourself attracted to God and the truths in the Bible, then you did not commit the unforgivable sin.
👉 So, becoming an Atheist, as in just ignore God, is forgivable if the person turns back to God, while alive.
👉 But committing the "unforgivable sin of the Spirit" by blaspheming against the Holy Spirit, is never forgivable. This person will further confirm they committed this sin by remaining in that rebellious state forever. They are not capable of turning back.
The unforgivable sin (Blasphemy against the Spirit) is never forgivable. It is when calling another person, who’s obviously filled with the holly Spirit, demon possessed. This attitude puts such persons, who made that accusation, in a state in which they cannot repent. As they cannot repent, God will not forgive them. But it is not the same as becoming an atheist. Because an atheist, while still alive, can repent and turn back to God. And God would accept and forgive her/him.